Background/Rationale: Millions of Veterans receive care from both VA and non-VA healthcare providers. Health information exchange (HIE) technologies are relatively new and are implemented across VA. HIE allows VA providers to send and receive medication data from non-VA medical institutions. This data exchange is important to coordinate patients' medications, reconcile medications to reflect what the patient is actually taking, and reduce the risk of adverse drug events. With the recent Veterans Access, Choice, and Accountability Act of 2014, it is even more critical to foster effective HIE that improves provider decision-making. Reports indicate, however, that VA's HIE technologies are inadequately supporting medication reconciliation tasks and are underutilized by providers. In addition, HIE medication data and VA medication orders are shown in separate displays, limiting the utility of HIE data and impeding providers' ability to coordinate medications. Objectives: The study objective is to identify providers' underlying cognitive needs in order to develop a set of technology design guidelines for presenting VA and HIE medication data. We hypothesize that, compared to current VA technologies, design guidelines from this research can significantly improve the quality and safety of providers' decision-making, including the efficiency and accuracy of medication reconciliation. Specific aims are as follows: Aim 1: Assess the strengths and weaknesses of VA's HIE interfaces for supporting providers' workflow and decision-making processes for medication reconciliation in the context of care. Aim 1 will yield an initial set of HIE design guidelines to support providers' workflow. Aim 2: Identify the cognitive strategies that providers use for medication reconciliation tasks. Aim 2 will yield an initial set of HIE design guidelines to support providers' cognition. Guidelines from Aims 1, 2 will be translated into a novel prototype for the VA-HIE interface. Aim 3: Evaluate the novel VA-HIE interface to assess whether the design guidelines significantly improve the quality and safety of providers' performance. Methods: For Aim 1, field observations, interviews, and remote usability tests will be conducted with inpatient and outpatient providers (prescribers and pharmacists) to generate a baseline, exploratory assessment of how well HIE interfaces support provider workflow. Qualitative data will be collected across four geographically dispersed VA Medical Centers. In Aim 2, card sorts and simulation interviews will be conducted with inpatient and outpatient providers to identify the underlying cognitive processes involved in medication reconciliation tasks. For Aim 3, we will conduct a randomized controlled trial with providers in a simulated environment and collect qualitative and quantitative data in order to evaluate whether the design guidelines significantly improves providers' efficiency and accuracy of medication reconciliation. Significance: This research will provide foundational knowledge on provider' cognition, which is necessary to ensure that VA and Veterans maximally benefit from VA's investment in HIE technologies. Study findings can be used to increase providers' adoption of HIE technologies and enhance the quality and safety of medication coordination for Veterans.